A vast array of geographic information is available today from numerous sources. These include topographic maps, aerial photographs, satellite imagery, laser scan point clouds, survey data, digital elevation models, mine plans, mine maps, hazard maps, radar data and others. In the mining field a mine operator may use several of these data sources when planning and operating a mine. The Inventors are particularly interested in open pit mines, but the issues discussed herein are applicable to underground mining as well as geographic visualisation tasks outside the mining industry.
There are generally two approaches for monitoring slopes in an open pit mine—targeted (tactical) monitoring and broad area (strategic) monitoring. Targeted monitoring is a tactical approach that is critical for monitoring existing slope movements posing a potential or immediate threat to the safety or productivity of mining operations. Broad area monitoring is a strategic approach that is helpful to detect ‘hot spots’ of movement activity even in areas that are not critical to current mine operations. This approach is helpful for planning, especially if areas are identified before they become closely or directly linked with active mining operations.
Slope stability radars have been generically described as either 3D radar or 2D radar. 3D radar (for example GroundProbe® SSR-XT) scans the slope in increments of azimuth, elevation and range, while 2D radar (for example GroundProbe® SSR-FX and SSR-SARx) scans the slope in increments of azimuth and range only. 3D radar is the preferred option for targeted (tactical) monitoring, and 2D radar for broad area (strategic) monitoring.
Most mines operate from a mine map that uses a mine coordinate system that may or may not be related to a real world coordinate system such as an ordinance survey grid reference or latitude and longitude. Mine operators seek to integrate other data sources, such as radar data and aerial photography, onto the mine coordinate system. Users however prefer to operate from visual cues rather than coordinate systems. Thus a mine manger may refer to a “bend in the haul road” or “the second bench” rather than a specific grid reference. There is therefore a need to present a visualisation of the mine site with accurate overlay of sources of geographic data.
In our original patent specification (see international patent publication WO 2002/046790) we addressed this desire by providing a visual image camera, a radar, and a process of coordinate registration to match the radar data to the visual image. This is useful if the radar data and visual data are from the same location, but it does not provide a mechanism for introducing other data sources unless a common geo-reference exists.
A current practice used by mine operators is to utilise qualified surveyors with sophisticated survey tools (such as total stations or differential GPS) to geo-reference the radar and radar data to the mine coordinate system, thereby enabling integration of disparate data. However, it can be costly and difficult to arrange for a qualified surveyor with expensive survey equipment to take the survey measurements when required, which causes delays in making key decisions around safety and productivity of the mine. Radar is an accepted safety best practice in mining and often mining cannot happen without radar monitoring; a delay in mining can cost millions of dollars per day in operating costs and lost production tonnes. This is especially true when radar systems are regularly moved around the mine to avoid blast damage or to monitor different mining areas using the same instrument.
An alternate practice is to use unqualified but more readily available personnel to use the same sophisticated survey tools that are integrated with the radar system to conduct the same task, but this adds more cost to the radar system and can introduce errors through incorrect use of these sophisticated survey tools.
For 2D and 3D radars operating at mine sites, the required spatial accuracy to geo-reference the radar data to the mine coordinate system does not need to be accurate to survey-quality (ie. within centimeters), rather in the order of meters is sufficient. This is because the spatial resolution of 2D and 3D radar systems depends on range and geometry, and is typically in the order of square meters rather than being points. Furthermore, slope movements occur over areas of the order of square meters on the slope face, so effort trying to geo-reference radar data to survey-quality points of centimeter accuracy in 3D space is wasted and inefficient.
In the current state of the art, radar data is combined with computer generated models called digital terrain maps (DTM) due to the current reliance on a limited number of proprietary data formats that contain geo-referenced coordinates. There is a wide range of other disparate data sources that are used by mines, such as photogrammetry data, aerial photos, lidar data, satellite data and the like. These disparate data sources often have proprietary data formats that are incompatible, some are 2D and others 3D, some are mine geo-referenced, others are not. Often disparate data sources are unable to be combined due to these inherent limitations, and currently are not combinable with radar data. There is great value synergy for mine operators to combine these disparate data formats together and with radar data. What is needed is the ability to combine these in a more simple way that references data sources to each other with or without a mine coordinate system. A simple method includes converting these to standard image formats such as jpg, gif, tiff, bmp, pdf and the like or to standard 3D formats, then combining them through the geo-positioning process.
An object of this invention is to geo-position data from two or more sources, one of which is preferably radar data, to within sufficient spatial accuracy for the application without the requirement for qualified surveyors or expensive survey tools, thereby reducing the cost and minimising delays.